Submitted thesis deal with estimation safeness of electroplating technologi with reference to occurrence hazardous substances falls on man and environment. To identification diversification was used quantitative risk assessment and chemical exposure index.

L’utilisation du chrome hexavalent pour le traitement de surface des matériaux de l’aéronautique est en passe d’être interdite par la réglementation REACH. Dans l’objectif de trouver une solution alternative, PROTEC industrie et le CEA travaillent en collaboration sur le développement d’une nouvelle solution sans-chrome permettant de remplacer les revêtements classiquement utilisés. Le travail de thèse présenté dans ce manuscrit s’inscrit dans le cadre du laboratoire commun MESTREL financé par le programme ANR Labcom, réunissant les deux entités citées ci-dessus. La solution proposée est basée sur le greffage d’un revêtement organique inspiré de la chimie des sels de diazoniums à la surface de l’Al2024-T3, alliage de référence du secteur aéronautique. Cette thèse vise initialement à déterminer les conditions pour lesquelles les propriétés du film greffé se rapprochent le plus de celles de son prédécesseur. Pour cela, des caractérisations spectroscopiques et électrochimiques des films greffés ont été réalisées. Les protocoles de microscopies électrochimiques développés ont notamment permis de sonder le niveau de passivation de la couche. La haute porosité du film greffé, nous a ainsi permis d’imaginer et de développer un système bicouche innovant combinant les propriétés anticorrosion des solutions actuelles aux hautes propriétés d’adhérence du film organique fonctionnalisé. En parallèle, une méthode de dépôt hors-cuve a été développée pour générer un gain économique important et faciliter le traitement de pièces de grandes dimensions. / The use of hexavalent chromium for anticorrosion surface treatments in aeronautics field will soon be banned by the REACH reglementation. Looking for an innovative solution, PROTEC industry and the CEA research center work in collaboration with the aim of developing a chromium free replacement treatment, which can substitute current solution and give competitive results both in adhesion and corrosion protection. The thesis project presented in this manuscript is part of a common laboratory named MESTREL, including the two entities. The proposed solution is based on the grafting of a polymeric film inspired by the diazonium chemistry on an Al2024-T3 surface, reference alloy in the aeronautic field. The principal objective of the thesis is to determinate the best conditions of grafting, -giving similar properties to chromium treatment. To this end, spectroscopic and electrochemical characterizations have been performed. Electrochemical Microscopy protocols are developed to assess the passivation properties of the film The high porosity of the film has allowed to develop a new innovative bilayer process combining anticorrosive properties of current solution and adhesion properties of the functionnal coating. At the same time, an out-of-tank deposition technique is developed. The goal is to enable economic benefits and facilitate treatment of very large aeronautic pieces.

[pt] Esta dissertação apresenta os resultados obtidos no processo de remediação de uma área contaminada por cromo hexavalente por meio da técnica de remediação química in situ (ISCR). A área de estudo localiza-se na cidade do Rio de Janeiro e foi ocupada por uma fábrica de vidros por cerca de quarenta anos e comprada para construção de condomínios residenciais. A área de estudo passou um processo de gerenciamento ambiental que contemplou diversos estudos ambientais para aquisição de dados e delimitar a contaminação, horizontal e verticalmente. O teste de bancada realizado com o reagente químico polissulfeto de cálcio demonstrou ser eficiente para reduzir as concentrações de cromo hexavalente em solo e água subterrânea. Com base nos dados adquiridos neste teste foi possível calcular a dose de injeção do polissulfeto de cálcio. Foram realizados setenta pontos de sondagem, pela técnica direct push, para injetar duzentos e cinquenta e dois mil e trinta litros de solução de polissulfeto de cálcio e água, sendo aproximadamente três mil e quinhentos litros por ponto de injeção. Os resultados após a injeção demonstraram que o polissulfeto de cálcio conseguiu remover o cromo hexavalente que estava adsorvido ao solo e reduziu a concentração de cromo hexavalente na água subterrânea entre quarenta e seis e sessenta e sete e noventa e nove e noventa e cinco por cento , após dezenove meses da injeção. Dessa forma, comprovou a eficiência deste reagente químico para remediação de áreas contaminadas por cromo hexavalente, assim como foi observado nos artigos técnicos de estudos de casos nos Estados Unidos e Europa. / [en] This dissertation presents the results obtained in the remediation process remediation of a contaminated area by hexavalent chromium applying the technology in situ chemical remediation (ISCR). The study area is located in the Rio de Janeiro city and was occupied by a glass factory for forty years and purchased for construction of residential condominiums. This dissertation presents the results obtained in the remediation process remediation of a contaminated area by hexavalent chromium applying the technology in situ chemical remediation (ISCR). The study area is located in the Rio de Janeiro city and was occupied by a glass factory for forty years and purchased for construction of residential condominiums. Chromium is an important metal for the industry and is used in various products and processes, such as electroplating, leather treatment, pulp, wood preservation, and refractory manufacturing. The trivalent chromium is essential from a nutritional point of view, non-toxic and poorly absorbed in the body, acting in the maintenance of some functions. Cr(III) is the most common being found and occurs naturally, since the element Cr(VI) can occur naturally, but in low concentrations, if the groundwater has geochemical conditions the Cr (III) can be oxidize to Cr (VI). The hexavalent chromium is the most dangerous valence state and, according to ATSDR (two thousand and twelve), have greater mobility in the groundwater, being carcinogenic by inhalation of high doses of soluble chromate salts. The mobility of hexavalent chromium is high in soil and groundwater because it is not adsorbed by the soil in that valence state, on the other hand when it is in trivalent form is strongly adsorbed by the soil, forming insoluble precipitates, having low mobility in soil and groundwater. The hexavalent chromium remediation by in situ chemical reduction using calcium polysulfide has been the subject of several field studies documented in the literature, both for soil and groundwater from the Chromite Ore Processing Residue (COPR) (Storch, et al., two thousand and two; Graham, et al., two thousand and six ; Charboneau, et al., two thousand and six ; Wazne, et al., two thousand seven a; Wazne, et al., two thousand seven b; Chrysochoou, et al., two thousand and ten ; Chrysochoou & Ting, two thousand and eleven ; Pakzadeh & Batista, two thousand and eleven ; Chrysochoou, et al., two thousand and twelve ). Calcium polysulfide is a fertilizer to soil and commercially available and has been used in some remediation studies cases for reducing hexavalent chromium in soil and groundwater. Being commercially available and used as fertilizer, it is a relatively cheap chemical reagent in comparison with other chemical compounds exclusively developed for this purpose. The stoichiometric demand and the chemical kinetics of the reduction of Cr (VI) by the calcium polysulfide in aqueous solution was studied by Graham et al. (two thousand and six) from the chromite ore processing residue (COPR). With this study it was reported that a molar ratio of a point sixty-six is required (close to the theoretical value of one point five) and a first-order kinetics with an initial concentration of twenty-six eight point mg/L and pH of the CPS solution around eleven point five, with the presence of oxygen. Thus, the hexavalent chromium is reduced to chromium hydroxide, slightly water soluble compound which is precipitated to the soil. The trivalent chromium has low solubility, toxicity, mobility, reactivity and is considered stable. There are various application techniques of chemical reagents in the underground environment, and choosing the most appropriate method for each area depends on the type of contaminant, geological environment, groundwater and surface interference, depth, thickness and size of the contaminated area. As described by Suthersan (mil novecentos ninety-six), the injection of chemical reagents has to achieve two objectives: (one) creating and maintaining an ideal redox environment and other parameters such as pH, presence or absence of dissolved oxygen, etc.; and (two) the delivery and distribution of the necessary reagents for a homogeneous way throughout the injection area, both horizontally and vertically. Thus, it is essential that the conceptual model of the study area is very detailed, so there is no doubt in the choice of chemical reagent application methodology. Although there are numerous laboratory studies on hexavalent chromium remediation using calcium polysulfide, there are few reports in the literature on the field application, especially case studies in Brazil, therefore, this case study becomes a demonstration applying calcium polysulfide as a remediation technique for hexavalent chrome, with geochemical data, which are important for monitoring chemical reduction. This case study shows the effectiveness, dosage and concentration of the study area, and may apply to other hexavalent chromium remediation projects. Materials and Methods A former glass factory (the Site ) operated in the North Zone of Rio de Janeiro / RJ, Brazil from the mid-thousand nine hundred and fifty s to two thousand and five. A portion of the facility was used to store raw material to produce glass, including arsenic oxide, and another portion of the Site was used to conduct industrial plating using hexavalent chromium (Cr(VI)) in the glass molds. In two thousand and nine, the Site was purchased for mixed use redevelopment, demanding an environmental assessment and subsequent remediation. Between two thousand and nine and two thousand and twelve several phases of site investigation was conducted. The results of the investigation indicated that Cr(VI) was present in soil at concentrations up to approximately twenty one mg/kg and in groundwater at concentrations up to approximately thirty mg/L. These concentrations exceeded regulatory criteria of three hundred mg/Kg for soil and zero point zero five mg/L for groundwater. A phased remedial approach was developed consisting of the following: (a) excavation and off-site disposal of two and four hundred ton of Cr(VI) impacted soil from the source area, performed in the unsaturated and saturated zone soils in the Cr(VI) source area; (b) post-excavation monitoring of the groundwater conditions; and (c) groundwater treatment following the excavation program. Hexavalent chromium concentrations in groundwater decreased significantly following the excavation, however, additional reduction of concentrations of Cr(VI) contaminant in groundwater was required. Then was designed and implemented a set of bench-scale treatability tests in order to evaluate groundwater remediation alternatives. Several proprietary and non-proprietary reductants for co-treatment of Cr(VI) were evaluated. Calcium polysulfide were selected to treat Cr(VI). To reduce residual Cr(VI) concentrations in the groundwater plume located downgradient of the former excavated source area, dois e seven hundred cubic meters were targeted for active treatment. The groundwater remediation approach consisted of the injection of thirty liters of CPS (twenty nine percent) diluted in two hundred and twenty liters of water, yielding a total of two hundred and fifty liters of solution injected using direct push technology into seventy two locations. Groundwater Monitoring As part of chemical reagent injection stage was performed the baseline monitoring with collection of soil and groundwater samples. The soil sampling was performed by direct push technique using PVC liner with two inches in diameter, to analyze the total and hexavalent chromium concentrations. Six months after the injection were installed sixteen monitoring wells, eight shallow wells (five meters) and eight deep wells (nine meters) spread upstream, side, middle and downstream of the injection area. Groundwater geochemical parameters (i.e., temperature, total solids dissolved, specific conductance, pH, oxidation-reduction potential, and temperature) were measured at the time groundwater samples were collected. Groundwater samples were collected and analyzed for total and dissolved chromium, hexavalent chromium, iron, arsenic, manganese, calcium, sulfate, and sulfide. Samples were field-filtered with disposable zero point forty-five μm polyethylene filter capsules prior to collecting samples for dissolved metals. Results and Discussion Dose calculations for the reduction of hexavalent chromium have been performed with the data obtained in the bench-scale treatability test and resulted in a stoichiometric demand of four mlCPS/kg soil to the treatment of the study area. Therefore thirty liters of solution was used containing twenty-nine percent calcium polysulfide and approximately two hundred and twenty two liters to perform their mixture, totaling two hundred and fifty-two thousand and thirty liters of solution. For solution injection were performed seventy two soil borings with eight point five meters deep, and the product was injected range between two point five and eightpoint five meters. The depth of injection was from two point five mbgl covered any change in water level due to seasonal variation. In each soil boring was injected chemical reagent solution comprised four hundred and seventeen liters of calcium polysulfide diluted in tree and eighty-three liters of water for a total volume of tree and a half liters of solution injected per point. The comparative analysis results of the third monitoring campaign ( eighteen months post-injection) with the baseline campaign (september/two thousand and twelve) indicated reduction of hexavalent chromium concentrations between forty-six point sixty-seven and ninety-nine and ninety-five percent. Regarding the second monitoring campaign (twelve months post-injection), the hexavalent chromium concentrations reduced between twenty-three point ninety-nine and ninety nine point seventy-nine percent in five of the fifteen monitoring wells that were sampled. In three of the fifteen monitoring wells the hexavalent chromium concentrations remained below the quantitation limit used by the analytical laboratory method. There was no increase in hexavalent chromium concentration, compared the results of the third and second monitoring campaign. The evaluation of the Eh and pH values measured in the monitoring campaigns showed that the pH value was in the acidic range (about four ) and after removal of contaminated soil with hexavalent chromium pH raised to between five and six, after the chemical reagent injection pH increased to the basic range (above seven point five). In the second and third campaign the pH reduced to acid range (below six point five), which can be regarded as the pH value of the area background. The Eh has inversely proportional behavior, increasing between the first and third campaign, and in the third campaign the measured values are in the ranges considered as moderately reducing (hundred to four hundred mV) and oxidizer (> four hundred mV). The pH variation also showed a relationship between increased concentrations of calcium, iron, manganese and sulfate (in some monitoring wells). There were also reductions in hexavalent chromium concentrations in monitoring wells. Conclusion This case study indicates that the use of different remediation techniques when applied together (excavation and chemical reduction), reducing the time required for remediation of a contaminated site without impacting the final cost of remediation. The chemical reduction of hexavalent chromium using calcium polysulfide was effective to reduce the concentration to less than the quantification limit of the analytical method used. Therefore, as presented it is necessary to carry out several studies to detail the hexavalent chromium concentration in the site, as well as understand the geochemistry of groundwater and performing bench-scale tests to evaluate the effectiveness of the chemical reagent in the site study hydrogeological environment and calculate the required dose. The treatability test with calcium polysulfide demonstrated the feasibility of using this chemical reagent by In Situ Chemical Reduction (ISCR) to reduce the hexavalent chrome concentration in soil and groundwater. The test resulted in a stoichiometric demand of four mlCPS /kg soil to the treatment of the study area. Soil samples collected six months after injection showed that the calcium polysulfide could desorb hexavalent chromium from the soil, since, contaminant concentrations were not detected in the samples. neteen months after the injection of the chemical reagent the groundwater concentrations of hexavalent chromium reduced from forty-six point sixty-seven to ninety-nine and ninety-five percent in relation to baseline campaign. And, of the fifteen monitoring wells in just three wells hexavalent chromium concentrations were detected. This demonstrates the effectiveness of using calcium polysulfide to remediate hexavalent chromium in soil and groundwater, confirming the studies by Storch et al. (two thousand and two), Graham et al (two thousand and six), Charboneau et al. ( two thousand and six), Wazne et al. (two thousand and seven a), Wazne et al. (two thousand and seven b), Chrysochoou et al. (two thousand and ten), Chrysochoou & Ting (two thousand and eleven), Pakzadeh & Batista (two thousand and eleven), Chrysochoou et al (2012) in several areas in United States and Europe.

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No description available.

Το χρώμιο (Cr) αποτελεί έναν από τους σημαντικότερους ρύπους του φυσικού περιβάλλοντος. Η ευρεία βιομηχανική χρήση του χρωμίου έχει ως αποτέλεσμα την απελευθέρωση μεγάλων ποσοτήτων του μετάλλου στο περιβάλλον κυρίως με τη μορφή του εξασθενούς χρωμίου (Cr(VI)). Το εξασθενές χρώμιο, μία από τις σταθερές μορφές του χρωμίου στο περιβάλλον, είναι ευδιάλυτο, υψηλά τοξικό, καρκινογενές και μεταλλαξιγόνο. Οι σύγχρονες μέθοδοι επεξεργασίας του εξασθενούς χρωμίου χρησιμοποιούν μικροοργανισμούς, στηριζόμενες στη μεταβολική και κυτταρική τους δράση. Πρόκειται για διεργασίες πιο ανταγωνιστικές, αποτελεσματικές και οικονομικές έναντι των συμβατικών φυσικοχημικών μεθόδων (χημική αναγωγή, ανταλλαγή ιόντων, διήθηση, ηλεκτροχημική επεξεργασία, προσρόφηση σε ενεργό άνθρακα, αντίστροφη όσμωση και μεμβράνες) καθώς παρουσιάζουν μικρές ενεργειακές απαιτήσεις, χαμηλό πάγιο και λειτουργικό κόστος και τέλος μικρότερη παραγωγή τοξικής λάσπης. Η βιολογική αναγωγή του εξασθενούς χρωμίου απαιτεί την παρουσία ενός δότη ηλεκτρονίων. Το ρόλο αυτό παίζει ο οργανικός άνθρακας, ο οποίος είναι απαραίτητος για την πραγματοποίηση της διεργασίας αυτής. Στην παρούσα διδακτορική διατριβή μελετήθηκε η επεξεργασία υγρών χρωμικών βιομηχανικών αποβλήτων, με ταυτόχρονη εκμετάλλευση/αξιοποίηση αγροτοβιομηχανικών παραπροϊόντων/αποβλήτων (μελάσα - χαμηλού κόστους και ορρός γάλακτος – μηδενικού κόστους), χρησιμοποιώντας βιολογικές μεθόδους. Αρχικά, πραγματοποιήθηκαν πειράματα για τη βελτιστοποίηση του ρυθμού αναγωγής των μεικτών αερόβιων γηγενών καλλιεργειών σε αντιδραστήρες αιωρούμενης ανάπτυξης. Στη συνέχεια χρησιμοποιήθηκε η μεικτή καλλιέργεια για τη μελέτη της βιολογικής αναγωγής του εξασθενούς χρωμίου σε αντιδραστήρες σταθερής κλίνης πιλοτικής κλίμακας με πλαστικό πληρωτικό υλικό, σε διάφορες λειτουργικές συνθήκες, στοχεύοντας στην μέγιστη απόδοση των συστημάτων και την αποφυγή λειτουργικών προβλημάτων. Το βιολογικό σύστημα που χρησιμοποιήθηκε στην παρούσα διδακτορική διατριβή, αποτελεί μία πολύ αποτελεσματική μέθοδο επεξεργασίας βιομηχανικών αποβλήτων επιβαρυμένων με το τοξικό εξασθενές χρώμιο, χρησιμοποιώντας οικονομικές πηγές άνθρακα όπως η μελάσα και ο ορρός γάλακτος. Η μέθοδος αυτή είναι πολλά υποσχόμενη, συνδυάζοντας υψηλά ποσοστά απομάκρυνσης με εξαιρετικά χαμηλές δαπάνες λειτουργικού κόστους. / Chromium is one of the most serious pollutants of natural environment. The widespread industrial use of chromium leads to the release of large quantities of this metal in the environment, mainly in the form of hexavalent chromium. The hexavalent chromium, one of the most stable forms that we can notice in the environment, is soluble, highly toxic carcinogenic and mutagenic. Contemporary water processing techniques of hexavalent chromium use micro-organisms, based on their metabolic and cellular activity. These procedures are more competitive, more effective and certainly financially affordable over the conventional physicochemical methods (chemical oxidation or reduction, ion exchange, filtration, electrochemical treatment, activated carbon adsorption, reverse osmosis and membrane technologies) as they show low energy demands, low maintenance cost and a smaller production of toxic mud. The biological reduction of hexavalent chromium requires the presence of an electron donor. This part is covered by organic carbon that is essential for carrying out the process. The present thesis studied the treatment of liquid industrial chromate waste and the exploitation/utilization of agroindustrial byproducts/wastewaters (molasses - low cost and cheese whey- zero cost), using biological methods. At the beginning, experiments were conducted to optimize the reduction rate of mixed aerobic indigenous cultures in suspended growth reactors. Subsequently, the mixed culture was used for the biological reduction of the hexavalent chromium, in laboratory pilot scale fixed bed reactors, with plastic media, in various functional conditions targeting to the maximum system performance and the prevention of functional problems. The biological system used in the present thesis constitutes a very effective method of processing industrial wastewater polluted with the toxic hexavalent chromium, by using affordable sources of carbon, such as molasses and cheese whey. This is a quite promising method, combining high removal rates with extremely low operating expenditure.

La détection sensible et sélective des métaux lourds, en particulier les métaux detransition, est d’une grande importance pour la santé publique ainsi que pour la surveillancede l’environnement. Les méthodes actuelles de référence, de par leur non portabilité, limitentla possibilité de disposer de mesures à haute résolution spatiale et temporelle. Lesmicrocapteurs optiques offrent un moyen attrayant et pratique pour surmonter ces limitationsde coût global et de temps d’analyse, en permettant la mesure en temps réel sur site.Pour démontrer ce potentiel, ces travaux de thèse sont orientés sur la détermination duchrome hexavalent Cr(VI) en solution à l’aide d’une réaction colorimétrique avec le 1,5-diphénylcarbazide (DPC), permettant de créer un complexe présentant un maximumd’absorption dans le domaine du visible. Ces travaux s’inscrivent dans la volonté dedévelopper un véritable laboratoire sur puce, intégrant la fonction fluidique parélectromouillage sur diélectrique pour créer la réaction colorimétrique, ainsi que la fonctionde mesure par intégration d’un capteur optique dédié à la mesure d’absorption dans desmicrovolumes (< μL). Pour la mesure d'absorption sur de si faibles volumes, l'utilisation demicrorésonateurs vise à augmenter de façon importante le chemin optique effectif et ainsi lasensibilité du capteur.Nous décrivons nos travaux sur la conception, la fabrication de la plateformemicrofluidique digitale ainsi que du résonateur optique en anneaux à des dimensionssubmicroniques par photolithographie par projection. Les matériaux polymères sontprivilégiés pour une intégration totale bas coût à terme, ainsi qu’un substrat verre, dont lespropriétés sont particulièrement adaptées aux applications optiques dans le domaine duvisible. / The selective and sensitive detection of heavy metals, such as transition metals, is ofparamount importance for health and safety an environmental monitoring. Current referencemethods, due to their lack of portability, are limiting factors to obtain high-resolution spatialand temporal data. Optical sensors offer an attractive and convenient way to overcome theselimitations of cost and time per analysis by offering real time, on-site measurementcapabilities.In order to demonstrate this potential, this thesis is focused on the detection and quantificationof hexavalent chromium Cr(VI) in water samples by a colorimetric reaction based on areaction with the 1,5-diphenylcarbazide (DPC), that produces a complex possessing anabsorption maximum in the visible range. This works endorse the goal of creating a true labon-chip, integrating both the fluidic function based on ElectroWetting on Dielectric (EWOD)to create the colorimetric reaction, and the sensing function based on the integration of anoptical sensor able to measure absorption variations in micro-volumes (< μL). In order toobtain sufficient sensitivity on such small volumes, optical microring resonators are used inthis work, due to their ability to enhance the effective optical path length by constructiveinterferences.This thesis describes the conception and fabrication of the EWOD microfluidic platform, aswell as the conception, simulation and fabrication of submicronic microring resonators usingstepper lithography. Polymer materials and glass substrates are selected, due to their greatoptical properties in the visible range, their compatibility with the EWOD platform, and theirintegrability at a reasonable cost.

Ph. D. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Driven by the need of sustainably sourced catalysts and the use of reaction systems that generate environmentally benign by-products, the present study aimed to deposit stable, dispersed palladium (Pd) nanoparticles on the modified surfaces of granular macadamia nutshell (MNS) biomass for catalytic reduction of hexavalent chromium [Cr(VI)] to trivalent chromium [Cr(III)]. Through wet impregnation with Pd(II) ions and subsequent hydrazine-mediated reduction to Pd(0), Pd nanoparticles were embedded in a scaffold of polyethyleneimine grafted on bleached MNS previously coated with a chemically bound layer of polyglycidyl methacrylate. Visualization and imagery from scanning electron microscopy showed the formation of different layers of the polymeric coating and dispersed palladium resulting from surface modification and palladium nanoparticle synthesis, respectively. X-ray diffraction, energy-dispersive X-ray spectroscopic analysis confirmed the formation of Pd on the modified MNS surface. An estimate of 5.0 nm for crystallite size was calculated by application of the Scherrer equation. The composite material, denoted Pd@PEI-MNS, exhibited catalytic activity in formic acid-mediated Cr(VI) reduction. Through a one-factor-at-a-time experimental design, the activity of the Pd@PEI-MNS was illustrated to be dependent on solution pH; initial Cr(VI) concentration, initial formic acid concentration, and presence of competing anions; Pd@PEI-MNS dose; and temperature. Subsequent modeling of the Cr(VI) removal process by response surface methodology revealed that the most influential factor was Pd@PEI-MNS dose followed by temperature and formic acid concentration. The influence of initial Cr(VI) concentration, was surpassed by the dose-temperature and dose-formic acid concentration interactive effects. Elucidation of the Cr(VI) removal mechanism by XPS and FTIR demonstrated the active participation of surface -CH2OH functional groups, the bulk of which originated from the reduction of esters of the grafted ligands. Replacement of formic acid to carbon dioxide, the -CH2OH groups were converted to -COO- groups.

Most developing countries are faced with drinking water problems, with conditions becoming more severe due to water pollution. Meeting the growing demands for clean water in most countries, there are difficult challenges as the availability and supply of drinkable water are diminishing. Due to economic and environmental concerns, development of additional physical means for the removal of organic compounds from wastewater using permanent magnets, electromagnetic coils, electrodes and ultrasonic pretreatment is desirable. Improving the adsorption and separation process, magnetic field exposure method has progressively drawn consideration. Magnetic field exposure method has demonstrated its capacity for increasing the adsorptive elimination of contaminants from water as static magnetization is suitable, simple and cost-effective. The polypyrrole magnetic nanocomposite use for adsorption experiments influenced by exter-nal magnetic field was prepared using the in-situ polymerization method, which was charac-terized using TEM, SEM, EDX, XRD, BET, FTIR, VSM, and ESR spectrophotometers. The magnetic nanocomposite (PPy/Fe3O4) was observed to have an average particle size of 10 nm with the elementary composition of carbon, oxygen, nitrogen, chloride and iron. The magnetic nanocomposite had a crystalline structure of face-centred cubic lattice of Fe3O4, an adsorption-desorption isotherm shape indicating a typical type-IV mesoporous material with a surface area of 28.77 m2/g. Characteristic peaks of Fe3O4 and PPy were also observed using FTIR spectro-photometer. From the VSM and ESR characterization, the synthesized superparamagnetic ma-terial was shown to have a saturation magnetization of 23 emu/g and an effective g-value of 2.25 g which was attributed to Fe3+ spin interaction. An enhanced removal of Cr(VI), fluoride and congo red dye were observed under the influence of magnetic field, with parameters like pH, adsorbent dosage, the initial concentration of ad-sorbate, magnetic field and magnetic exposure time been varied. The enhanced adsorption of contaminants using magnetic field is attributed to the increase in the magnetic field induced on the particles over a magnetic exposure time, resulting in the rotating particles forming aggre-gates due to the increased magnetic force and torque on the particles from the PSV results. This leads to increase in the chain collision and area of particle interaction with the aqueous solution of hexavalent chromium, fluoride and congo red dye. / Physics / Ph. D. (Physics)

Made available in DSpace on 2017-07-10T18:08:10Z (GMT). No. of bitstreams: 1 Neiva Martin.pdf: 2565426 bytes, checksum: 9ed40e36b9798ff30f3a52b416d705e9 (MD5) Previous issue date: 2008-10-08 / In this work, the chromium ions bioaccumulation experiment was carried out using three species of aquatic macrophytes: Salvinia auriculata, Pistia stratiotes and Eicchornia crassipes, in order to confirm the hexavalent chromium detoxification during the biosorption process. Previously, a chromium speciation test based on chemical extraction of trivalent chromium from hexavalent chromium-doped hydroponic solutions was also performed at different pH, in order to verify if the nutritive solution pH could be responsible by the natural reduction of oxidation state on chromium before the biosorption process by the plants. No reduction from Cr(VI) to Cr(III) was observed at all solution pH. Based on the peculiar characteristics of High Resolution X-ray Fluorescence technique (HR-XRF), which allows to measure the X-ray Kß spectral line energy with good energy resolution (around 2,0 eV) for the transition metal region, the change on oxidation state of hexavalent chromium was possible to study through the Kß1,3, Kß2,5 and Kß spectral lines, which bring up information on chromium oxidation state and chemical environment. The HR-XRF measurements were performed at the XRD1 vacuum chamber available in the National Laboratory of Synchrotron Light, located near Campinas city. After collection, dry roots and chromium compound standard were prepared in compact disk by pressing. Each sample disk, spherical curved analyzer, and radiation detector were placed in a circle of Rowland within an arrangement of Johann. Another radiation detector was also used to monitoring of monochromatic X-ray beam intensity during the measurements. All the samples were irradiated by a 6.1 keV monochromatic X-ray beam. All the emission spectra were normalized to the monitor counts, and subtracted the organic matrix contribution and chromium absorption edge. Based on the spectral Kß2,5 peak intensity of roots and standard samples, the total chromium uptake concentration in plant was calculated, indicating that there is approximately 1.0 % of chromium per dry biomass after 27 days of experiment. When both Cr-Kß spectra of macrophytes roots with Cr(III) and Cr(VI) treatment were compared, their spectral Kß2,5 peak were identical in energy and width for the three aquatic plants, suggesting that the chromium reduction from hexavalent to trivalent form have occurred in all cases studied. The peak width at half maximum for Kß2,5 in all root samples were slightly larger than the chromium compound samples, which can be explained by the fact that there is the possibility to have different ligands to chromium ions inside the biological structure of roots. Based on these results, the chromium detoxification from hexavalent to trivalent form have actually happened during the biosorption of chromium into the macrophytes roots. Finally, these aquatic macrophytes have a great potential to detoxificate and accumulate of chromium ions that can be very useful to the metal removal from industrial effluents. / Neste trabalho foi feito o experimento de bioacumulação do cromo trivalente e hexavalente por três espécies de macrófitas aquáticas: Salvinia auriculata, Pistia stratiotes e Eicchornia crassipes, visando verificar a ocorrência do processo de redução do Cr(VI) durante a biossorção. Previamente, um teste de especiação de cromo baseado em extração química do cromo trivalente a partir de uma solução hidropônica dopada com cromo hexavalente, foi realizado em diferentes pHs, para verificar se o pH da solução nutritiva pode ser o responsável pela redução natural do estado de oxidação do cromo antes do processo de biossorção pelas plantas. Não foi observada a redução do Cr(VI) para Cr(III) no pH da solução de cultivo. Pelas características da técnica de Fluorescência de Raios-X de Alta Resolução em Energia (HR-XRF), que permite medir a energia das linhas espectrais de raios X Kß com alta resolução em energia (em torno de 2,0 eV) para a região dos metais de transição, foi possível estudar a mudança do estado de oxidação do cromo hexavalente através das linhas espectrais Kß1,3, Kß2,5 e Kß , que traz informação sobre o estado de oxidação do metal e seu ambiente químico. As medidas de HR-XRF foram realizadas na câmara de vácuo XRD1, no Laboratório Nacional de Luz Síncrotron, em Campinas. Após a coleta, discos compactados de raízes secas e padrões de compostos de cromo foram preparados. Cada disco de amostra, o analisador esférico, e o detector de radiação foram acomodados em um círculo de Rowland com arranjo de Johann. Durante as medidas, um detector foi usado para monitorar a intensidade do feixe de raios X monocromáticos incidentes. Todas as amostras foram irradiadas com feixe monocromático de 6,1 keV. Os espectros de emissão foram normalizados pelas contagens do monitor, e subtraída as contribuições da matriz orgânica e da borda de absorção do cromo. Baseado na intensidade da linha espectral K&#946;2,5 das amostras de raízes e padrões, a concentração de cromo total nas plantas foi calculada, indicando que esta é de aproximadamente 1,0% por biomassa seca após 27 dias de experimento. Os espectros de emissão Cr-Kß das raízes das macrófitas tratadas com Cr(III) ou Cr(VI) foram comparados, e as suas linhas espectrais K&#946;2,5 mostraram-se idênticas em energia e largura para as três plantas aquáticas, sugerindo que a redução do cromo, de hexavalente para trivalente, ocorreu em todos os casos estudados. A largura do pico para a linha espectral Kß2,5 em todas as amostras de raízes mostrou-se maior que nas amostras de compostos de cromo, o que pode ser explicado pelo fato de que é possível haver diferentes ligantes para o íon cromo na estrutura orgânica das raízes. Baseado nesses resultados, a redução do Cr(VI) para Cr(III) ocorreu durante o processo de biossorção do cromo pelas raízes das macrófitas aquáticas. Desta forma, verifica-se que estas macrófitas têm um grande potencial para detoxificar e acumular íons cromo, podendo ser utilizada com eficiência na remoção de metais em efluentes industriais.